Process fob vulcanizing pneumatic tires



w. SEWARD.

PROCESS FOR VULCANIZING BNUEMATIC -TlRES.

APPLICATION FILED SEPT. 22. 1919.

1,380,426, 'Patented'JuneZ 1921.

2 SHEETS-SHEET 2.

UNITED STATES PATENT OFFICE.

PROCESS FOR VULGANIZING PNEUMATIC TIRES.

I Application filed September 22, 1919. Serial No. 325,505.

T 0 all whom it may concern:

Be it known that 1, WILLIAM SEWARD, a citizen of the United States, residing at Baltimore city, State of Maryland, have invented certain new and useful Improvements in Processes for Vulcanizing Pneumatic Tires, of which the following is a specification.

This invention relates to the art of vulcanizing or curing rubber and analogous prod nets, and more particularly to the vulcanization or cure of the outer casing or the shoe of pneumatic tires.

The object of the invention is to improve the vulcanizing or curing process, and thereby obtain a better product and one less liable to be defective.

In order that the invention may be better understood, reference is had to the accompanying drawings, forming a part of this specification, and in said drawings,

Figure 1 is a sectional view of the apparatus employed in carrying out the invention;

Fig. 2 is a horizontal section on the line 22 of Fig. 1, and

Figs. 3 and 4 are sectional views'showing modifications of the apparatus.

' The prevailing standard method of manufacturing pneumatic tire casings consists in building the casings on a form or core to proper dimensions and gages, according to their particular specification before being finally vulcanized and finished. The casing is then ready to be placed in a mold, or an exterior container or former of outside con tour, for the final process of vulcanization or curing. This final process consists in subjecting the mass of rubber and rubberized fabric comprising the casing to a certain degree of heat for a certain period. The heat is obtained from any suitable source, usually steam, which is introduced into a receptacle known as a heater or vulcanizing pot in which the molds containing the casings to be treated are placed. A plurality of molds, in superimposed relation, is placed in the heater and pressed and. held together firmly by hydraulic pres sure. Such a heater is shown in the drawings fat 5, and the mold} units inclosed therein at 6, the latter being supported on the head or table 7 of a hydraulic ram 8. The mold units are pressed up against the top9 of theheater by the hydraulic pressure transmitted by the ram 8 and its head 7.,

Specification of Letters Patent.

Patented J une7, 1921.

Each mold unit is composed of two superimposed sections 10 and 11, respectively.

p A tire casing may be formed and cured in several ways. By the wrapped tread process the exterior contour is produced by wrapping plies of fabric over and around the casing which has previously been built up on an iron core; or the casing can be cured by what is known as the full molded process. Another process is termed the air ba process, and there is also practised w at is known as the hydraulic cure which is merely the substitution of a volume of water forced into the casing and held there during vulcanization, thus exercising the same function as a metal core or an air bag, these functions being theact of determining the inner dimensions of the tire casing, whether such dimensions are determined by the rigid iron core within the casing, or by the internal air, water or gaseous pressure 7 maintained throughout the vulcanizing period in the individual mold containing the casing to be cured.

These processes are all lacking in a sureness ofresult, so far as a perfect and uniform product is concerned; 6. 9.:

Unless all dimensions and gages are essentially correct, a full molded or a wrapped tread casing will show what is termed buckles or waves in the fabric plies. Ifthe material contained between the inner core and the outer mold or outer wrapping is excessive or'if it is not quite sufficient or up to gage, a faulty product is the result. a

In using the air bag system, the core upon which the casing has been built is removed and an air bag is introduced to replace the same during vulcanization. The airbag contains air or steam under pressure. This method eliminates waves, buckles, etc., but it is uncertain and hazardous, for if the bag bursts under pressure, a defective product is the result; or lack of internal pressure from any cause will result in a casing not completely fillin athe mold; or the leakage or reduction 0 any internal pressure will cause a retardation of vulcanization at some point. In either case. the product isrendered defective.

Many methods have been tried in the en deavor to overcome the hazard ofthe air bag method, which is the preferred method as it produces the most excellent type of tire casing, but all efforts have been confined to the endeavor to isolate and confine necessary internal pre sure to the individual tire casing, whether such pressure is transmitted from the outside oi the heater or is contained within the casing; in an air bag or an air container, assisted at times by the pressure resulting roml vaporization of water introduced before vul *anization has begun, but which is raised above the boiling point during vulcanization.

The present invention has for its object the elimination or all manutacturine losses attending the faults and hazards of any and all of the present known methods. It entirely eliminates buclfles, waves and other defects resulting from the full molded process; it is more economical and surcr of good results than the wrapped process, and it insures a perfect product when applied to the air bag process. The invention also renders unnecessary the bolting together of the mold units in order to retain the pressure in the air bag, and it makes unnecessary any nesting of mold units by cross bars and long bolts. The invention also renders unnecessary a pressure retainingvalve on the individual air lung itself, and it does away with the expensive and. generally unsatisi actory method of maintaining pressure in an air bag, by means of a pressure transmitting, device such as a tubing" or piping to the individual bag, and it will. prolong the life ot any to a point where the present very considerable cost per casing: cured on an air bag is reduced to most insignificant fi ure.

In carrying out the present inven on, th molds 6 for the tire casings 12 are made absolutely air-tight on the outside of the latter by any means, such the introduction of suitable gasrrets 13 between the contiguous faces of the sections 10 and 1.1 of the molds, these gaskets beingadjacent to the inner and outer circuinterences oi the molds. Each mold unit (3 also is formed with an internal overflow chamber 15 of proper and predetermined cubic contents, so that the normal and natural tunctions of the mold may be carried on so far as its ability to expel tragpcd air or excess stock is concerned. ln connection with this mold structure an air bag 16 is used having a tree and open inlet 17 to the interior of the vulcanizing chamber or pot 5. The mold units 6 are held by the ram 8 as hereinbefore described.

It will be evident from the foregoing that the fluid pressure and heat in the chamber 5 enters the bag 16 through the inlet 17, whereby the bag is distended to expand the casing 12 to the wall. of the mold 6. The fluid pressure and heating medium in the chamber 5 is obtained from any suitable source, and it is composed of compressed air and steam in combination. As the mold is held together air tight, the pressure in the chamber 5 entering the bag 16 provides all necessary internal pressure by which to properly form up the casing, and the heat iron the steam, properly controlled by heat regulating devices, will furnish any desired vulcanizing' temperature. The use of the composite gaseous fluid consisting of compressed air and steam as the pressure and heating mediums, results in an action which is radically dilierent from the action of steam alone, for the reason that by the former any desired pressure at any temperature is readily obtainable. As is well known, the temperature of steam is governed by its pressure; or, con -xersely, the pressure of steam depends on its temperature. l/Vater, at any temperature below bo ling point, does not exert any pressure is :le from its weight, or unless it is confined and subjected to pressure. By the use of air as the pressure producing medium and steam as the heating medium, it is possible to obtain in the vulcanizaer a temperature of say, 290 degrees F. and a pressure 01"? one hundred pounds, or in "fact any pres sure at any temperature contingent only on the strength of the container, a condition absolutely impossible to obtain with the use of wat or steam. Steam alone always has a certain pressure according to its temperature, and hence it a ressure of say, eighty pounds at a temperature of 290 degrees 1 is desired in the vuicanizer, the use of steam alone would not produce this result, as steam at a temperature of 290 degrees F. has a pressure of only forty-lire pounds, ap-

proximately. However, by using steam at the stated. temperature, and combining til erewith air compressed to a degree to produce a pressure equal to the difference between the steam pressure at 290 degrees F. pounds) and the desired pressure of eighty pounds, it is possible to obtain en tirely satisfactory results. Tie pressure or": steam alone at a temperature necessary for a successful vulcanizing operation is en tirely insuliicient.

A. further advantage arising from the use of steam and compressed air is that for any redetermined cubic content there is present only agproximately lifty per cent. as much moisture aswould be contained in the same space were it filled with steam alone, and as the vulcanizing period procoeds, a maintenance of temperature and pressure will automatically reduce the moisture percentage. In the event of accident to the steam supply, the air pressure will. still exert sufficient internal pressure in the tire casing within the mold to pre vent collapse thereof. Furthermore, by the use 01"- steam alone, the condensation thereof will produce a partial vacuum, whereas the composite gaseous fluid (steam and air) employed in the present process will not act in this manner, due to the presence of the air, and it will give absolutely any combination of temperature and pressure which may be desired to fulfil the many varying heats and pressures necessary in vulcanizing processes. The number and combinatitons of pressure and temperature possible to obtain is practically infinite, whereas water or steam alone have positive and absolute limitations.

The mold can be built in a usual and standard manner, but instead of the usual and necessary overflow cavity being prepared, which leads finally to the outside of the mold, and instead of the usual method of permitting excess stock or trapped air to escape into and through the usual overflow cavity to the outside of the mold, the present invention contemplates the expelling of such excess into the internal overflow chamber 15, the latter being within the outer gasket 13 hereinbefore mentioned. The flow of excess stock or trapped air may be started by external mold pressure or internal fluid pressure, but it must find an outlet, and hence it will be forced and finally make its way into the chamber 15. As the pressure contained in the chamber is normal and atmospheric, it will permit of certain compression, and as the internal pressure in the vulcanizer is greater, and as this greater pressure has entered the bag 16, room is thus provided in the chamber 15 for any excess stock or any trapped air.

The invention also permits absolute elimination of the air bag. This is done by combining with the mold 6, an inner head forming ring 18 shown in Fig. 3. This ring is shaped to conform to any desired contour of the inner sides of the beads of the tire casing, and it is placed naturally within the protection of the inner sealing gasket 13. The ring 18 has openings 19 for admitting the fluid pressure to the inside of the tire casing 12 to distend the same in the same manner this was done by the air bag 16, and expelling all excess and trapped air into the internal overflow chamber 15 as before.

Fig. 4 shows a mold 6 for tire casings in which the carcass and the tread are separately made and then united, the process being known as the double cure. No air bag is used, and the fluid pressure enters the casing 12 within the mold through ports 20 in the latter.

The apparatus disclosed in the present application is claimed in a copending application, Serial No. 325,504, filed Sept. 22, 1919.

I claim:

1. The process of vulcanizing a tire casing in a mold located in a vulcanizing chamber, consisting in supplying a gaseous fluid pressure and steam to the interior of" the chamber, and permitting such fluid pressure and steam to enter the interior of the tire casing for distending the same in the mold.

2. The process of vulcanizing a tire casing in a mold located in a vulcanizing chamber, consisting in supplying a gaseous fluid pressure and steam to the interior of the chamber, permitting such fluid pressure and steam to enter the interior of the tire casing for distending the same in the mold, and excluding said fluid pressure and steam from the mold cavity containing thetire casing.

3. The process of vulcanizing a tire casing in a mold located in a vulcanizing chamber, consisting in supplying a gaseous fluid pressure and steam to the interior of the cham-,

ber, permitting such fluid pressure and steam to enter the interior of the tire casing for distending the same in the mold, permitting escape of excess stock and trapped air, and excluding the gaseous fluid pressure and steam of the vulcanizing chamber fromthe mold cavity containing the tire casing and from the escape chamber.

4:. The process of vulcanizing a tire casing in a mold located in a vulcanizing chamber, consisting in fitting the interior of the tire casing with an inflatable bag, supplying a gaseous fluid pressure and steam to the interior of the chamber, and permitting such gaseous fluid pressure and steam to enter the bag to inflate the same and distend the tire casing in the mold.

In testimony whereof I aflix my signature in the presence of two witnesses.

WILLIAM SEWARD.

Witnesses:

E. WALTON BREWINGTON, HOWARD D. ADAMS. 

